I remember seeing an NFL Films piece on him, evidently he was considered one of the dirtiest, nastiest players of his era. His game was to get in your head and take your focus away (much like the more well-known Conrad Dobler in later years). Even his team mates hated him -- in the piece I mentioned, Chuck Bednarik had a profanity laced tirade about what a dirty so-and-so Kilroy was. Like most NFL Films pieces, it was very entertaining.